using System.Text.Json;

namespace HellionChat.Themes;

internal static class ThemeJsonWriter
{
    public static string Serialize(Theme theme)
    {
        using var ms = new MemoryStream();
        using (var writer = new Utf8JsonWriter(ms, new JsonWriterOptions { Indented = true }))
        {
            writer.WriteStartObject();
            writer.WriteNumber("schemaVersion", ThemeJsonLoader.SupportedSchemaVersion);
            writer.WriteString("slug", theme.Slug);
            writer.WriteString("name", theme.Name);
            writer.WriteString("author", theme.Author);
            writer.WriteString("description", theme.Description);

            writer.WriteStartObject("colors");
            WriteColor(writer, "primaryDark", theme.Colors.PrimaryDark);
            WriteColor(writer, "primary", theme.Colors.Primary);
            WriteColor(writer, "primaryLight", theme.Colors.PrimaryLight);
            WriteColor(writer, "primaryGlow", theme.Colors.PrimaryGlow);
            WriteColor(writer, "accentDark", theme.Colors.AccentDark);
            WriteColor(writer, "accent", theme.Colors.Accent);
            WriteColor(writer, "accentLight", theme.Colors.AccentLight);
            WriteColor(writer, "identity", theme.Colors.Identity);
            WriteColor(writer, "windowBg", theme.Colors.WindowBg);
            WriteColor(writer, "childBg", theme.Colors.ChildBg);
            WriteColor(writer, "frameBg", theme.Colors.FrameBg);
            WriteColor(writer, "surface", theme.Colors.Surface);
            WriteColor(writer, "surfaceHover", theme.Colors.SurfaceHover);
            WriteColor(writer, "border", theme.Colors.Border);
            WriteColor(writer, "textPrimary", theme.Colors.TextPrimary);
            WriteColor(writer, "textMuted", theme.Colors.TextMuted);
            WriteColor(writer, "textDim", theme.Colors.TextDim);
            WriteColor(writer, "statusSuccess", theme.Colors.StatusSuccess);
            WriteColor(writer, "statusDanger", theme.Colors.StatusDanger);
            WriteColor(writer, "statusWarning", theme.Colors.StatusWarning);
            WriteColor(writer, "statusInfo", theme.Colors.StatusInfo);
            writer.WriteEndObject();

            writer.WriteStartObject("layout");
            writer.WriteNumber("windowRounding", theme.Layout.WindowRounding);
            writer.WriteNumber("childRounding", theme.Layout.ChildRounding);
            writer.WriteNumber("popupRounding", theme.Layout.PopupRounding);
            writer.WriteNumber("frameRounding", theme.Layout.FrameRounding);
            writer.WriteNumber("grabRounding", theme.Layout.GrabRounding);
            writer.WriteNumber("tabRounding", theme.Layout.TabRounding);
            writer.WriteNumber("scrollbarRounding", theme.Layout.ScrollbarRounding);
            writer.WriteNumber("windowBorderSize", theme.Layout.WindowBorderSize);
            writer.WriteNumber("frameBorderSize", theme.Layout.FrameBorderSize);
            writer.WriteEndObject();

            // Typography always written so a hand-edited file shows the
            // available knobs even when the user has not picked any
            // override yet.
            writer.WriteStartObject("typography");
            WriteOptionalFloat(
                writer,
                "overrideGlobalFontSizePt",
                theme.Typography.OverrideGlobalFontSizePt
            );
            WriteOptionalFloat(
                writer,
                "overrideSymbolsFontSizePt",
                theme.Typography.OverrideSymbolsFontSizePt
            );
            writer.WriteEndObject();

            if (theme.ChatColors is { Channels.Count: > 0 } cc)
            {
                writer.WriteStartObject("chatChannels");
                foreach (var kvp in cc.Channels)
                    writer.WriteString(kvp.Key.ToString(), $"#{kvp.Value:X8}");
                writer.WriteEndObject();
            }

            writer.WriteEndObject();
        }

        return System.Text.Encoding.UTF8.GetString(ms.ToArray());
    }

    private static void WriteColor(Utf8JsonWriter writer, string key, uint rgba)
    {
        writer.WriteString(key, $"#{rgba:X8}");
    }

    private static void WriteOptionalFloat(Utf8JsonWriter writer, string key, float? value)
    {
        if (value.HasValue)
            writer.WriteNumber(key, value.Value);
        else
            writer.WriteNull(key);
    }
}